The present invention relates to a package comprising a moisture-sensitive substance, such as a 2-cyanoacrylate-based composition, as packed in a container comprising a metal foil-based laminated film as one constituent material.
2-Cyanoacrylate-based quick-setting or instantaneous adhesives have rapid curability and therefore have come into wide use as industrial or domestic adhesives.
When applied to adherends, 2-cyanoacrylate-based quick-setting adhesives are rapidly cured by means of moisture in the air by the mechanism of anionic polymerization. This means that when such adhesives are packed in containers for the purpose of distribution, the container material selected should be sufficiently low in moisture permeability and the inside wall material to be in contact with the contents should be free of any additive that may promote anionic polymerization.
Among various resins, polyethylene has the lowest moisture permeability. In the case of low-density polyethylene, the moisture permeability per 30 xcexcm is about 19 g/m2xc2x724 hrs, for instance, and, in the case of high-density polyethylene, it is about 5 g/m2xc2x724 hrs, for instance. When the film thickness is increased, the moisture permeability decreases in proportion to the thickness. It is also possible to mold polyethylene into containers without adding molding additives such as a lubricant. In these circumstances, polyethylene containers made by blow molding and having a required thickness are generally used as containers for 2-cyanoacrylate-based quick-setting adhesives.
Since aluminum is excellent in ductility, a raw material aluminum slab can be made up into a tubular container by placing said slab in a die and applying thereto an instantaneous pressure by means of a punch. The moisture permeability of aluminum is substantially close to zero and much lower than those of polyethylene species as mentioned above. Therefore, tubular aluminum containers are also generally used as containers for 2-cyanoacrylate-based quick-setting adhesives.
2-Cyanoacrylate-based quick-setting adhesives are packed in medium portions (e.g. 20 g or 30 g) or large portions (e.g. 50 g or 100 g) into containers and placed on the market. They are also put on the market in portions not larger than 10 grams, especially in portions not larger than 5 grams, in many instances. This is because, in many cases, only a very small amount of a 2-cyanoacrylate-based quick-setting adhesive is used in each use thereof for repairing or constructing an article and because once the nozzle opening is opened, the contents may be cured within the nozzle opening after the lapse of many days until the next occasion of use.
The above-mentioned blow-molded polyethylene containers or tubular aluminum containers are used also as containers for 2-cyanoacrylate-based quick-setting adhesives packed in small portions such as 10 grams or less, in particular 5 grams or less, or 2 grams or 3 grams. In the case of small capacity products, however, the internal surface area per gram of a quick-setting adhesive is relatively large and therefore the storage stability of the quick-setting adhesive tends to decrease a the volume of the contents decreases, raising a problem to be solved because of the products being small-sized ones.
Thus, when blow-molded polyethylene containers are used for small-sized products, the use of low-density polyethylene as the polyethylene may secure squeezability owing to its elasticity, but leads to an impairment in stability of the contents because of its moisture permeability. Therefore, it is necessary, in producing blow-molded small capacity containers, to use high-density polyethylene lower in moisture permeability. However, blow-molded high-density polyethylene containers are rigid and therefore, in the case of small-sized products, the squeezability of containers with a small diameter is sacrificed and, even when the sidewall portion of each container is pressed by means of fingers, the contents are hardly squeezed out. When compared with tubular aluminum containers, high-density polyethylene containers are markedly inferior in moisture permeation preventing ability and, when the wall thickness of such containers is increased for further reducing the moisture permeability, the squeezability becomes worsened. It is also a practice to attach the level comprising an aluminum vapor-deposited film with an adhesive layer to a blow-molded high-density polyethylene container. This is, however, only for the purpose of display and/or indication and no effect can be expected in reducing the moisture permeability of the container.
On the contrary, tubular aluminia containers are substantially impermeable to moisture and therefore favorable to the storage stability of quick-setting adhesives. However, when the sidewall portion is pressed with fingers, they fail to restore the initial shape due to the nature of the material. Thus, when the contents have a low viscosity, it is difficult to control the amount to be squeezed out, hence an excess amount may readily be squeezed out. When the contents have a high viscosity, there arises a substantial problem in that the containers are inconvenient for handling in squeezing out the contents, for example the contents may drip after squeezing out due to the residual pressure. A technique is conceivable which comprises inserting a polyethylene tube into a tubular aluminum container to thereby provide the container with restoring ability (repulsiveness). This technology, however, necessarily increases the cost.
Aluminum-based laminated tubes made of a laminated film having the layer constitution polyethylene layer/aluminum foil/substrate film layer are known for packaging foodstuffs and other articles, although they are not concerned with containers for 2-cyanoacrylate-based quick-setting adhesives. When such aluminum-based laminated tubes are applied to containers for such a quick-setting adhesive, the quick-setting adhesive leaking through the polyethylene layer necessarily causes interfacial peeling between the polyethylene layer and aluminum foil.
With such background art, the present invention has for its objects to provide a package comprising a moisture-sensitive substance, such as a 2-cyanoacrylate-based composition, packed in a container, which package has practical storage stability owing to the low moisture permeability of the container even when said package is a small-sized product which a small fill of the contents and which package is easy to handle in squeezing out the contents when they are liquid, since the container has squeezability (deformability and restoring ability) and which package also has a light shielding effect and is advantageous from the cost viewpoint.
The package according to the present invention comprises the contents L comprising a moisture-sensitive substance as packed in a container 1 and is characterized in that said container 1 is provided, on the outside surface of the main sidewall portion 11 thereof, with a metal foil-containing laminated film B by welding so that said laminated film may cover at least the whole surface of said main sidewall portion 11.